1. Field of the Invention
The present invention relates to a method of automatically adjusting a determination voltage used in an induction type power supply system and a determination voltage adjustment device thereof, and more particularly, to a method of automatically adjusting a determination voltage and a determination voltage adjustment device thereof capable of amplifying strength of a feedback signal of the induction type power supply system, in order to enhance sensitivity for signal interpretation.
2. Description of the Prior Art
For the purposes of safety, a power supply device of an induction type power supply system has to ensure that a proper power receiving device is positioned on the supplying-end coil of the power supply device and ready to receive power before power is supplied. In order to allow the power supply device to identify whether the power receiving device is accurate, a data code should be transmitted for identification purposes. The data code transmission is performed via the following steps: the power supply device first drives the supplying-end coil to generate resonance and sends electromagnetic power to the power receiving device in order to transmit power. When the power receiving device receives the power, the power receiving device may change the impedance on the receiving-end coil via the signal modulation technology, and the variations are fed back to vary the amplitude of carriers on the supplying-end coil. The signals of the supplying-end coil are then converted into digital information to be transmitted to a supplying-end microprocessor for interpretation via a circuit. The variations in amplitude of carriers on the supplying-end coil, however, are quite weak and easily interfered with by noise, so that such variations may not easily be extracted and converted into accurate logic signals in digital form. In the prior art, the industry provides a method of using active band-pass filters, couplers and voltage comparators composed of multiple operational amplifiers to perform the signal conversion. Such a design is complex and difficult to manufacture. U.S. application Ser. No. 13/212,564 provides a simplified filter composed of resistors and capacitors to output signals to a voltage comparator. The comparator compares the signals with a predetermined voltage level to output digital signals. Such a circuit is simple and easily manufactured.
The above circuit structure in the prior art still has some drawbacks, however. After the carried signals on the supplying-end coil are transmitted to the signal analysis circuit to perform half-wave rectification, the variations are attenuated by half. If there is no amplifier, the small signal may not easily be identified. The reference voltage of the comparator is generated via two voltage-dividing resistors connected to the power terminal and the ground terminal, respectively. The resistor elements may possess errors during manufacture, which may cause a deviation on the defined voltage level. The reference voltage and the normal voltage of the signal therefore cannot be too close; otherwise, a wrong signal may be output due to the errors in resistance values. Since the reference voltage cannot be close to the normal voltage, the sensitivity for signal interpretation may also be decreased. In the prior art, in order to recognize and trigger both positive and negative signals, two comparators are required to set two reference voltages to act as upward and downward triggers for the signals. Since there are errors in the resistance elements, the comparators will be harder to manufacture and set. The prior art may only determine the trigger signals from the power receiving end and transform the trigger signals to a digital data code, but the signal strength of data cannot be estimated. When the signal is weak, the system cannot insert power on the signal to enhance the signal strength. If the coil cannot be coupled well, the signal transmission capability may easily be lost.
Thus, there is a need for improvement over the prior art.